JP5996594B2 - Pilot and data transmission in MIMO (multiple input multiple output) systems applying subband multiplexing - Google Patents

Description

(Claiming priority under USP 119)
This patent application is assigned to this assignee and is hereby expressly incorporated by reference, filed on June 16, 2005, “Pilot and Data Transmission in Quasi-Orthogonal Single Carrier Frequency Division Multiple Access System ( Provisional Application No. 60 / 691,701 entitled “PILOT AND DATA TRANSMISSION IN A QUASI-ORTHOGONAL SINGLE-CARRIER FREQUENCY DIVISION MULTIPLE ACCESS SYSTEM” and “Quasi-Orthogonal Single Carrier Frequency Division” filed on July 22, 2005 Provisional application serial number 60 / 702,033 entitled “PILOT AND DATA TRANSMISSION IN A QUASI-ORTHOGONAL SINGLE-CARRIER FREQUENCY DIVISION MULTIPLE ACCESS SYSTEM”, filed on August 22, 2005 Pilot and data transmission in a quasi-orthogonal single carrier frequency division multiple access system (PILOT AND DATA TRANSMISSIO NIN A QUASI-ORTHOGONAL SINGLE-CARRIER FREQUENCY DIVISION MULTIPLE ACCESS SYSTEM) "and claims priority to the provisional application serial number 60 / 710,366.

  The present disclosure relates generally to communication, and more specifically to pilot and data transmission in a wireless communication system.

  A multiple access system communicates simultaneously with multiple terminals on the forward and reverse links. The forward link (or downlink) refers to the communication link from the base stations to the terminals, and the reverse link (or uplink) refers to the communication link from the terminals to the base stations. Multiple terminals may simultaneously transmit data on the reverse link and / or receive data on the forward link. This is often accomplished by multiplexing multiple data transmissions on each link to be orthogonal to one another in time, frequency and / or code domain. Perfect orthogonality between multiple data transmissions is typically not achieved in most cases due to various factors such as channel conditions, receiver imperfections, and the like. Nevertheless, orthogonal multiplexing ensures that each terminal's data transmission minimizes interference with other terminals' data transmission.

  The number of terminals that can communicate with the multiple access system at any given moment is typically limited by the number of information channels available for data transmission and then by the available system resources. For example, the number of information channels includes the number of orthogonal code sequences available in a code division multiple access (CDMA) system, the number of frequency subbands available in a frequency division multiple access (FDMA) system, and time division multiple access (TDMA). It can be determined by the number of time slots available in the system and the like. In many cases, it is desirable to allow more terminals to communicate with the system at the same time to improve system capacity.

  Thus, there is a need in the prior art for techniques to support simultaneous transmission for more terminals in a multiple access system.

  Described herein are pilot transmission, channel estimation and spatial processing techniques that support simultaneous transmission for terminals in a single carrier frequency division multiple access (SC-FDMA) system. SC-FDMA systems can either (1) interleaved FDMA (IFDMA) to transmit data and pilot on subbands distributed over a frequency band or system bandwidth, or (2) a group of adjacent subbands. A localized FDMA (LFDMA) system for transmitting data and pilot over, or (3) enhanced FDMA (EFDMA) for transmitting data and pilot over multiple groups of adjacent subbands . IFDMA is also called distributed FDMA, and LFDMA is also called narrowband FDMA, classical FDMA, and FDMA.

  For pilot transmission, a number of transmitters can be time division multiplexed (TDM), code division multiplexed (CDM), interleaved frequency division multiplexed (IFDM), or localized frequency division multiplexed as described below. (LFDM) can be used to transmit these pilots. The pilots from these transmitters are then orthogonal to each other, which allows the receiver to derive a higher quality channel estimate for each transmitter.

  For channel estimation, the receiver performs complementary demultiplexing (demultiplexing) for pilots sent by the transmitter using TDM, CDM, IFDM or LFDM. The receiver may derive a channel estimate for each transmitter using, for example, a minimum mean square error (MMSE) technique, a least squares (LS) technique, or some other channel estimation technique. The receiver may also perform filtering, thresholding, truncation, and / or tap selection to obtain an improved channel estimate.

  The receiver also performs receiver spatial processing on data transmissions received from the transmitter on the same time / frequency block. The receiver may derive a spatial filter matrix based on channel estimates for the transmitter and using, for example, zero-forcing (ZF), MMSE, or maximum ratio combining (MRC) techniques.

  Various aspects and embodiments of the invention are described in further detail below.

1 is a diagram illustrating a Q-FDMA system with multiple transmitters and one receiver. FIG. FIG. 3 shows an exemplary subband structure for IFDMA. FIG. 3 shows an exemplary subband structure for LFDMA. FIG. 3 illustrates an exemplary subband structure for EFDMA. FIG. 6 is a diagram illustrating generation of IFDMA, LFDMA, or EFDMA symbols. It is a figure which shows the production | generation of an IFDMA symbol. It is a figure which shows a frequency hopping (FH) system. It is a figure which shows a TDM pilot system. It is a figure which shows a CDM pilot system. It is a figure which shows a dispersion | distribution / localization pilot system. FIG. 2 shows a distributed pilot for two transmitters with IFDMA. FIG. 2 shows a distributed pilot for two transmitters with LFDMA. FIG. 3 shows localized pilots for two transmitters with IFDMA. FIG. 3 shows localized pilots for two transmitters with LFDMA. FIG. 6 shows a transmission with different data and pilot symbol durations. FIG. 2 shows a process for transmitting pilots and data in a Q-FDMA system. FIG. 6 shows a process for performing channel estimation. It is a figure which shows H-ARQ transmission. FIG. 3 shows H-ARQ transmission for two transmitters. It is a block diagram of a transmitter. It is a block diagram of a receiver.

  The features and nature of the present invention will become more apparent from the following detailed description when considered in conjunction with the drawings in which like reference characters identify correspondingly throughout.

  The term “exemplary” is used herein to mean “serving as an example, instance, or illustration”. Any embodiment or design described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments or designs.

  The pilot transmission, channel estimation and spatial processing techniques described herein may be used for various communication systems. For example, these techniques include SC-FDMA systems that use IFDMA, LFDMA, or EFDMA, orthogonal frequency division multiple access (OFDMA) systems that use orthogonal frequency division multiplexing (OFDM), other FDMA systems, other OFDM-based Can be used for system etc. Modulation symbols are sent in the time domain with IFDMA, LFDMA and EFDMA and in the frequency domain with OFDM. In general, these techniques may be used for systems that utilize one or more multiplexing schemes for the forward and reverse links. For example, the system may: (1) SC-FDMA (eg IFDMA, LFDMA or EFDMA) for both forward and reverse links, (2) One version of SC-FDMA (eg LFDMA) for one link, for the other link Another version of SC-FDMA (eg IFDMA), (3) MC-FDMA for both forward and reverse links, (4) SC-FDMA for one link (eg reverse link), the other link (eg forward link) MC-FDMA (eg, OFDMA) for (directional link), or (5) some other combination of multiplexing schemes. SC-FDMA, OFDMA, some other multiplexing scheme, or a combination thereof may be used on each link to achieve the desired performance. For example, SC-FDMA and OFDMA can be used for one given link, SC-FDMA is used in some subbands and OFDMA is used in other subbands. It may be desirable to use SC-FDMA on the reverse link to achieve lower PAPR and relax power amplifier requirements for the terminal. It may be desirable to use OFDMA on the forward link to potentially achieve higher system capacity.

  The techniques described herein may be used for the downlink and uplink. These techniques also include (1) an orthogonal multiple access system in which all users in a given cell or sector are orthogonal in time, frequency and / or code, and (2) many users in the same cell or sector are the same It can also be used for quasi-orthogonal multiple access systems that can transmit simultaneously on the same frequency in time. For clarity, much of the description below is for a quasi-orthogonal SC-FDMA system, also called a Q-FDMA system. Q-FDMA systems support spatial division multiple access (SDMA) that uses multiple antennas located at different spatial points to support simultaneous transmission for multiple users.

  FIG. 1 shows a Q-FDMA system 100 having multiple (M) transmitters 110a-110m and one receiver 150. For simplicity, each transmitter 110 is equipped with a single antenna 134 and the receiver 150 is equipped with multiple (R) antennas 152a-152r. For the forward link, each transmitter 110 may be part of a base station and receiver 150 may be part of a terminal. For the reverse link, each transmitter 110 may be part of a terminal and receiver 150 may be part of a base station. A base station is generally a fixed station and may also be referred to as a base transceiver system (BTS), an access point, or some other terminology. A terminal can be fixed or mobile and can be a wireless device, a cellular phone, a personal digital assistant (PDA), a wireless modem card, and so on.

  At each transmitter 110, transmit (TX) data and pilot processor 120 encodes, interleaves, and symbol maps the traffic data and generates data symbols that are modulation symbols for the traffic data. The modulation symbol is a complex value related to one point in the signal point arrangement, for example, M-PSK or M-QAM. The processor 120 also generates pilot symbols that are modulation symbols for the pilot. SC-FDMA modulator 130 multiplexes data symbols and pilot symbols, performs SC-FDMA modulation (eg, for IFDMA, LFDMA, or EFDMA) and generates SC-FDMA symbols. The SC-FDMA symbol may be an IFDMA symbol, an LFDMA symbol, or an EFDMA symbol. The data SC-FDMA symbol is an SC-FDMA symbol for traffic data, and the pilot SC-FDMA symbol is an SC-FDMA symbol for pilot. A transmitter unit (TMTR) 132 processes (e.g., converts to analog, amplifies, filters (filters), frequency upconverts) the SC-FDMA symbols and transmits the radio frequency (RF) modulated signal via antenna 134. Is generated.

  In receiver 150, R antennas 152a-152r receive RF modulated signals from transmitters 110a-110m, and each antenna provides the received signal to an associated receiver unit (RCVR) 154. Each receiver unit 154 conditions (eg, filters, amplifies, frequency downconverts, and digitizes) its received signal and provides input samples to a receive (RX) spatial processor 160. RX spatial processor 160 estimates the channel response between each transmitter 110 and the R antenna based on the pilot received from each transmitter. RX spatial processor 160 also performs receiver spatial processing for each subband used by multiple transmitters to split the data symbols sent by these transmitters. RX spatial processor 160 further demultiplexes (demultiplexes) the SC-FDMA symbols received for each transmitter. An SC-FDMA demodulator (Demod) 170 performs SC-FDMA demodulation on the detected SC-FDMA symbols for each transmitter and provides data symbol estimates for the transmitter. An RX data processor 172 symbol demaps, deinterleaves, and decodes the data symbol estimates for each transmitter and provides decoded data for this transmitter. In general, the processing by receiver 150 is complementary to the processing by transmitters 110a-110m.

  Controllers 140a-140m and controller 180 direct the operation of various processing units at transmitters 110a-110m and receiver 150, respectively. The memories 142a to 142m and the memory 182 store program codes and data for the transmitters 110a to 110m and the receiver 150, respectively.

  System 100 can utilize IFDMA, LFDMA, or EFDMA for transmission. The subband structure and symbol generation for IFDMA, LFDMA and EFDMA are described below.

FIG. 2A shows an exemplary subband structure 200 for IFDMA. The total system bandwidth of BW MHz is divided into a number (K) of orthogonal subbands given indices 1 to K. Here, K can be any integer value. For example, K may be equal to a power of 2 (eg, 64, 128, 256, 512, 1024, etc.) that may simplify the transformation between the time domain and the frequency domain. The spacing between adjacent subbands is BW / K MHz. For simplicity, the following description assumes that all K total subbands are available for transmission. For subband structure 200, the K subbands are arranged in S disjoint or non-overlapping interlaces. The S interlaces are disjoint in that each of the K subbands belongs to only one interlace. In one embodiment, each interlace includes N subbands uniformly distributed across all K subbands, and consecutive subbands in the interlace are spaced apart by S subbands. Be placed. Here, K = S · N. For this embodiment, the interlace u includes subbands u, S + u, 2S + u,..., (N−1) · S + u. here

It is. The index u is an interlace index, and is also a subband offset indicating the first subband in this interlace. In general, a subband structure can include any number of interlaces, each interlace can include any number of subbands, and these interlaces can include the same or different numbers of subbands. Can do. Further, N may or may not be an integer divisor of K, and the N subbands may be uniformly distributed over all K subbands or may be unevenly distributed.

FIG. 2B shows an exemplary subband structure 210 for LFDMA. With respect to subband structure 210, all K subbands are arranged in S non-overlapping groups. In one embodiment, each group includes N subbands adjacent to each other, and group v includes subbands (v−1) · N + 1 to v · N. Where v is the group index,

It is. N and S for subband structure 210 may be the same as or different from N and S for subband structure 200. In general, a subband structure can include any number of groups, each group can include any number of subbands, and a group can include the same or different number of subbands.

  FIG. 2C shows an exemplary subband structure 220 for EFDMA. With respect to subband structure 220, all K subbands are arranged in S non-overlapping sets, each set including G groups of subbands. In one embodiment, the K total subbands are distributed into S sets as follows. The K total subbands are first divided into a number of frequency ranges, each frequency range including K '= K / G consecutive subbands. Each frequency range is further divided into S groups, where each group includes V consecutive subbands. For each frequency range, the first V subband is assigned to set 1, the next V subband is assigned to set 2, and so on, and the last V subband is assigned to set S. The set s as s = 1,..., S includes subbands having an index k satisfying (s−1) · V ≦ k modulo (K / G) <s · V. Each set includes a G group of V consecutive subbands, or a total of N = G · V subbands. In general, a subband structure can include any number of sets, each set can include any number of groups and any number of subbands, and a set can include the same or different numbers of subbands. it can. For each set, the group can include the same or different number of subbands and can be uniformly or non-uniformly distributed across the system bandwidth.

  SC-FDMA systems can also utilize a combination of IFDMA, LFDMA and / or EFDMA. In one embodiment, multiple interlaces may be formed for each subband group, and each interlace may be assigned to one or more users for transmission. For example, two interlaces can be formed for each subband group, the first interlace can include subbands with even numbered indexes, and the second interlace can be odd numbered indexes. May include subbands having In another embodiment, multiple subband groups can be formed for each interlace, and each subband group can be assigned to one or more users for transmission. For example, two subband groups may be formed for each interlace, the first subband group may include lower subbands in the interlace, and the second subband group may be interlaced. Of the upper subbands. IFDMA, LFDMA, EFDMA and combinations thereof can be considered as different versions of SC-FDMA. For each version of SC-FDMA, a large number of users may divide a subband set into a number of subsets and assign each subset to each user for pilot transmission (eg, interlace or subband). Pilots that are orthogonal on the group) can be transmitted.

FIG. 3A illustrates the generation of IFDMA symbols for one interlace, or LFDMA symbols for one subband group, or EFDMA symbols for one subband set. The original sequence of N modulation symbols to be transmitted in one symbol period on an interlace, subband group or subband set is denoted as {d ₁ , d ₂ , d ₃ ,..., D _N }. (Block 310). The original sequence is transformed to the frequency domain by an N-point discrete Fourier transform (DFT) to obtain a sequence of N frequency domain values (block 312). N frequency domain values are mapped to the N subbands used for transmission, and KN zero values are the remaining KN to generate a sequence of K values. Mapped to subbands (block 314). The N subbands used for transmission are in a group of adjacent subbands for LFDMA (as shown in FIG. 3A) and K total subbands for IFDMA. It is in one interlace with subbands distributed across the band (not shown in FIG. 3A) and for EFDMA it is in one set of multiple groups of subbands (also in FIG. 3A). (Not shown). The series of K values is then transformed to the time domain by a K-point inverse discrete Fourier transform (IDFT) to obtain a series of K time-domain output samples (block 316).

  The last C output samples of the sequence are copied to the first part of the sequence to form an IFDMA, LFDMA, or EFDMA symbol containing K + C output samples (block 318). The C copied output samples are often called cyclic prefix (cyclic prefix) or guard interval (protection interval), where C is the cyclic prefix length. Cyclic prefixes are used to combat intersymbol interference (ISI) caused by frequency selective fading, which is a frequency response that varies across the system bandwidth.

FIG. 3B shows IFDMA symbol generation for one interlace where N is an integer divisor of K and N subbands are evenly distributed across all K subbands. The original sequence of N modulation symbols to be transmitted in one symbol period on N subbands in interlace u is denoted as {d ₁ , d ₂ , d ₃ ,..., D _N }. (Block 350). The original sequence is replicated S times to obtain an extended sequence of K modulation symbols (block 352). N modulation symbols are sent in the time domain and collectively occupy N subbands in the frequency domain. The S copies of the original sequence are N pieces spaced by S subbands by zero power S-1 subbands separating adjacent occupied subbands. Result in subbands occupied by. The extended sequence has a comb frequency spectrum occupying interlace 1 in FIG. 2A.

The extended sequence is multiplied by a phase ramp to obtain a frequency transformed sequence of K output samples (block 354). Each output sample in the frequency transform sequence may be generated as follows.

Where n = 1, ..., K
Where d _n is the n th modulation symbol in the extended sequence, x _n is the n th output sample in the frequency conversion in the sequence, u is the index of the first subband in the interlace. The multiplication with the phase ramp e ^{−j2π · (n−1) · (u−1) / K} in the time domain is performed so that the frequency transformation sequence occupies the interlace u in the frequency domain and the comb frequency of the extended sequence The spectrum is shifted upward in frequency. The last C output samples of the frequency transform sequence are copied to the first part of the frequency transform sequence to form an IFDMA symbol that includes K + C output samples (block 356).

  The IFDMA symbols are periodic in the time domain (except for the phase ramp) and therefore occupy N equally spaced subbands starting from subband u. S IFDMA symbols may be generated with S different subband offsets. These S IFDMA symbols occupy different interlaces and will therefore be orthogonal to each other.

  The process shown in FIG. 3A can be used to generate IFDMA, LFDMA, and EFDMA symbols for any value of N and K. The process shown in FIG. 3B may be used to generate IFDMA symbols when N is an integer divisor of K and N subbands are evenly distributed across all K subbands. . The IFDMA symbol generation in FIG. 3B does not require DFT or IDFT and may therefore be preferred. FIG. 3A may be used to generate IFDMA symbols when N is not an integer divisor of K, or when N subbands are unevenly distributed across the K subbands. IFDMA, LFDMA, and EFDMA symbols may be generated in other ways.

  K + C output samples of an SC-FDMA symbol (which can be an IFDMA, LFDMA or EFDMA symbol) are transmitted in K + C sample periods, one output sample per sample period. The SC-FDMA symbol period (or simply symbol period) is the duration of one SC-FDMA symbol and is equal to the K + C sample period. The sample period is also called the chip period.

  As generally used herein, one subband set is one interlace for IFDMA, or one subband group for LFDMA, or one set of multiple subband groups for EFDMA. One set of possible subbands. For the reverse link, S users transmit data and pilot simultaneously to the base station without interfering with each other on S subband sets (eg, S interlaces or S subband groups). obtain. Multiple users can also share a given subband set, and the base station may use receiver spatial processing to isolate interfering transmissions on this subband set. For the forward link, the base station may transmit data and pilot simultaneously on S subband sets to S users without interference.

  FIG. 4 shows a frequency hopping (FH) scheme 400 that can be used for the forward and / or reverse link. Frequency hopping can provide frequency diversity and randomization of interference from other cells or sectors. With frequency hopping, a user may be assigned an information channel associated with a hop pattern that indicates which subband set (if any) should be used in each time slot. Hop patterns are also called FH patterns or sequences, and time slots are also called hop periods. A time slot is the amount of time spent on a given subband set and typically spans multiple symbol periods. The hop pattern can pseudo-randomly select different subband sets in different time slots. Frequency diversity is achieved by selecting all or many of the S subband sets over a certain number of time slots.

  In one embodiment, one channel set is defined per link. Each channel set includes S information channels that are orthogonal to each other so that the two information channels are not mapped to the same subband set in any given time slot. This prevents intra-cell / sector interference between users assigned to information channels in the same channel set. Each information channel is mapped to a particular series of time / frequency blocks based on the hop pattern for this information channel. A time / frequency block is a specific set of subbands in a specific time slot. Up to S users for this embodiment can be assigned S information channels and will be orthogonal to each other. Multiple users can also be assigned the same information channel, and these overlapping users will share the same sequence of time and frequency blocks and will always interfere with each other. In this case, the pilots for the overlapping users can be multiplexed as follows, and the data transmission for these users is received in the receiver space as also described below. It can be split using processing.

  In another embodiment, multiple channel sets are defined per link. Each channel set includes S orthogonal information channels. The S information channels in each channel set may be pseudo-random with respect to the S information channels in each of the remaining channel sets. This randomizes interference between users assigned to information channels in different channel sets.

  FIG. 4 shows an exemplary mapping of information channel 1 in each channel set to a sequence of time / frequency blocks. The information channels 2 to S in each channel set may be mapped to vertically and cyclically shifted versions of the time / frequency block sequence for information channel 1. For example, information channel 2 in channel set 1 may be mapped to subband set 2 in time slot 1, to subband set 5 in time slot 2, to subband set 1 in time slot 3, and so on.

  In general, a large number of users may overlap in a deterministic manner (eg by sharing the same information channel), a pseudo-random manner (eg by using two pseudo-random information channels), or a combination of both .

1. Pilot Transmission Quasi-orthogonal SC-FDMA allows many transmitters to transmit on a given time / frequency block. Data transmissions from these transmitters can interfere with each other and can be separated using receiver spatial processing even though these data transmissions are not orthogonal to each other. Pilot transmissions from these transmitters may be orthogonalized using TDM, CDM, IFDM, LFDM, or some other multiplexing scheme. Orthogonal pilots improve channel estimation, which in turn can improve data performance because channel estimates are used to recover data transmission. In general, any number of transmitters (eg, 2, 3, 4 etc.) can share one predetermined time / frequency block. For simplicity, the following description assumes that Q = 2 and that pilot transmissions from two transmitters are multiplexed on the same time / frequency block. Also for simplicity, pilots for IFDMA and LFDMA only are described below.

  FIG. 5 shows a TDM pilot scheme. Transmitters 1 and 2 transmit data and pilot on the same time / frequency block consisting of one set of N subbands in one time slot of T symbol periods with T> 1. As an example shown in FIG. 5, the transmitter 1 transmits data in symbol periods 1 to t−1, then transmits a pilot in symbol periods t, and then transmits data in symbol periods t + 2 to T. The transmitter 1 transmits neither data nor pilot in the symbol period t + 1. The transmitter 2 transmits data in symbol periods 1 to t-1, then transmits pilots in symbol period t + 1, and then transmits data in symbol periods t + 2 to T. The transmitter 2 transmits neither data nor pilot in the symbol period t. Data transmissions from transmitters 1 and 2 interfere with each other. Pilot transmissions from transmitters 1 and 2 do not interfere with each other, so improved channel estimates can be derived from each transmitter. Each transmitter (1) transmits a data SC-FDMA symbol in each symbol period designated for data transmission and (2) a pilot SC-FDMA symbol in each symbol period designated for pilot transmission. Can do. A pilot IFDMA symbol may be generated as shown in FIG. 3A or 3B based on a sequence of N pilot symbols. A pilot LFDMA symbol may be generated as shown in FIG. 3A based on a sequence of N pilot symbols.

  FIG. 6 shows a CDM pilot scheme. As an example shown in FIG. 6, each transmitter transmits data in symbol periods 1 to t−1, then transmits pilots in symbol periods t and t + 1, and then transmits data in symbol periods t + 2 to T. . Transmitters 1 and 2 transmit pilots simultaneously in symbol periods t and t + 1. Each transmitter generates pilot SC-FDMA symbols in the normal manner, for example as shown in FIG. 3A or 3B. Transmitter 1 is assigned an orthogonal pilot code of {+ 1, + 1}, multiplies its pilot SC-FDMA symbol by +1 during symbol period t, and pilot SC-FDMA by +1 during symbol period t + 1. Multiply symbols. Transmitter 2 is assigned an orthogonal pilot code {+1, -1}, multiplies its pilot SC-FDMA symbol by +1 during symbol period t, and -1 by pilot SC during symbol period t + 1. Multiply FDMA symbols. The radio channel is assumed to be stationary over the two symbol periods used for pilot transmission. The receiver combines the SC-FDMA symbols received during symbol periods t and t + 1 to obtain the pilot SC-FDMA symbols received for transmitter 1. The receiver subtracts the SC-FDMA symbol received in symbol period t + 1 from the SC-FDMA symbol received in symbol period t to obtain the pilot SC-FDMA symbol received for transmitter 2.

  For the embodiment shown in FIGS. 5 and 6, two symbol periods are used for TDM or CDM pilots from two transmitters. Each transmitter transmits its pilot over one symbol period for the TDM pilot scheme and over two symbol periods for the CDM pilot scheme. Each transmitter may have a certain maximum transmit power level that may be imposed by regulatory agencies or design limits. In this case, the CDM pilot scheme allows each transmitter to transmit its pilot over a longer time interval. This allows the receiver to collect more energy for the pilot and derive a higher quality channel estimate for each transmitter.

  FIG. 7 shows a distributed / localized pilot scheme. As an example shown in FIG. 7, each transmitter transmits data in symbol periods 1 to t−1, then transmits a pilot in symbol period t, and then transmits data in symbol periods t + 1 to T. Both transmitters 1 and 2 transmit pilots simultaneously in the symbol period t. However, the pilots for transmitters 1 and 2 are multiplexed using IFDM or LFDM as described below and do not interfere with each other. As used herein, a distributed pilot is a pilot sent on subbands distributed across an interlace or subband group, and a localized pilot is sent on adjacent subbands within an interlace or subband. Pilot. Distributed pilots for multiple users may be multiplexed to be orthogonal within a given interlace or subband group using IFDM. Localized pilots for multiple users may be multiplexed to be orthogonal within a given interlace or subband group using LFDM.

  FIG. 8A shows distributed pilots for transmitters 1 and 2 with IFDMA, also called distributed IFDMA pilots. The N subbands in the interlace u are indexed 1 to N and are divided into two subsets. The first subset includes subbands having odd numbered indexes, and the second subset includes subbands having even numbered indexes. The subbands in each subset are spaced by 2S subbands, and the subbands in the first subset are offset by S subbands from the subbands in the second subset. Transmitter 1 is assigned a first subset having N / 2 subbands and transmitter 2 is assigned a second subset having N / 2 subbands. Each transmitter generates a pilot IFDMA symbol for the assigned subband subset and transmits this IFDMA symbol on the subband subset.

  The IFDMA symbol for the distributed pilot may be generated as follows.

  1. Form an original sequence of N / 2 pilot symbols.

  2. Duplicate the original sequence 2S times to generate an extended sequence with K pilot symbols.

  3. Apply a phase ramp for interlace u as shown in equation (1) to obtain a frequency transform sequence.

  4). In order to generate a pilot IFDMA symbol, a cyclic prefix is added to the frequency conversion sequence.

  FIG. 8B shows distributed pilots for transmitters 1 and 2 with LFDMA, also called distributed LFDMA pilots. The N subbands in subband group v are given indices 1 to N and are divided into two subsets. The first subset includes odd numbered indexes and the second subset includes even numbered indexes. The subbands in each subset are spaced by two subbands, and the subbands in the first subset are offset by one subband from the subbands in the second subset. Transmitter 1 is assigned a first subset having N / 2 subbands and transmitter 2 is assigned a second subset having N / 2 subbands. Each transmitter generates a pilot LFDMA symbol for the assigned subband subset and transmits this LFDMA symbol on the subband subset.

  The LFDMA symbol for the distributed pilot may be generated as follows.

  1. Form an original sequence of N / 2 pilot symbols.

  2. DFT is performed on N / 2 pilot symbols to obtain N / 2 frequency domain values.

  3. N / 2 frequency domain values are mapped to N / 2 pilot subbands in the assigned subset, and zero values are mapped to K-N / 2 remaining subbands.

  4). A K-point IDFT is performed on the K frequency domain values and zero values to obtain a series of K time domain output samples.

  5. A cyclic prefix is added to the time domain sequence to generate a pilot LFDMA symbol.

  Alternatively, the LFDMA symbols for the distributed pilot may be the original of N / 2 pilot symbols to generate an extended sequence of N pilot symbols that may be processed as previously described with respect to FIG. 3A. It can be generated by duplicating the sequence.

  As shown in FIGS. 8A and 8B, the distributed pilots for transmitters 1 and 2 occupy different subband subsets and therefore do not interfere with each other. The receiver performs complementary processing to recover the distributed pilot from each transmitter as follows.

  FIG. 9A shows localized pilots for transmitters 1 and 2 with IFDMA, also called localized IFDMA pilots. The N subbands in the interlace u are indexed 1 to N and are divided into two subsets. The first subset includes subbands 1-N / 2 in the lower half of the system bandwidth, and the second subset includes subbands N / 2 + 1-N in the upper half of the system bandwidth. The subbands in each subset are spaced by S subbands. Transmitter 1 is assigned a first subset having N / 2 subbands and transmitter 2 is assigned a second subset having N / 2 subbands. Each transmitter generates a pilot IFDMA symbol for the assigned subband subset and transmits this IFDMA symbol on the subband subset.

  IFDMA symbols for localized pilots may be generated as follows.

  1. Form an original sequence of N / 2 pilot symbols.

  2. Duplicate the original sequence S times to generate an extended sequence with K / 2 pilot symbols.

  3. DFT is performed on K / 2 pilot symbols to obtain K / 2 frequency domain values. N / 2 frequency domain values are non-zero and the remaining frequency domain values are zero for S iterations.

  4). Map the K / 2 frequency domain values such that N / 2 non-zero frequency domain values are sent on the N / 2 pilot subbands in the assigned subset.

  5. Map zero values to the remaining subbands.

  6). A K-point IDFT is performed on the K frequency domain values and zero values to obtain a series of K time domain output samples.

  7). A cyclic prefix is added to the time domain sequence to generate a pilot IFDMA symbol.

  Steps 3-6 above are similar to the steps performed to generate an LFDMA symbol assigned K / 2 subbands from all K subbands.

  FIG. 9B shows localized pilots for transmitters 1 and 2 with LFDMA, also referred to as localized LFDMA pilots. The N subbands in subband group v are given indices 1 to N and are divided into two subsets. The first subset includes subbands 1 to N / 2 in the lower half of the subband group, and the second subset includes subbands N / 2 + 1 to N in the upper half of the subband group. The subbands in each subset are adjacent to each other. Transmitter 1 is assigned a first subset having N / 2 subbands and transmitter 2 is assigned a second subset having N / 2 subbands. Each transmitter generates a pilot LFDMA symbol for its subband subset and transmits this LFDMA symbol on the subband subset.

  The LFDMA symbol for the localized pilot may be generated as follows.

  1. Form an original sequence of N / 2 pilot symbols.

  2. DFT is performed on N / 2 pilot symbols to obtain N / 2 frequency domain values.

  3. N / 2 frequency domain values are mapped to N / 2 pilot subbands in the assigned subset, and zero values are mapped to K-N / 2 remaining subbands.

  4). A K-point IDFT is performed on the K frequency domain values and zero values to obtain a series of K time domain output samples.

  5. A cyclic prefix is added to the time domain sequence to generate a pilot LFDMA symbol.

  The above steps 1 to 5 are for the generation of LFDMA symbols to which N / 2 subbands are allocated from all K subbands.

  For clarity, exemplary methods for generating distributed pilots with IFDMA and LFDMA and generating localized pilots with IFDMA and LFDMA have been described above. Distributed and localized pilots may be generated in other ways. Distributed and localized pilots may be generated for EFDMA in a manner similar to that described above, eg, for IFDMA and LFDMA.

  FIGS. 8A-9B illustrate the case where Q = 2 and each transmitter is assigned N / 2 subbands for pilot transmission. In general, N subbands within a given time / frequency block can be assigned to Q users in any way. Q users may be assigned the same number of subbands or different numbers of subbands. Each user may be assigned N / Q subbands if Q is an integer divisor of N and approximately N / Q subbands if Q is not an integer divisor of N. For example, if N = 16 and Q = 3, three transmitters can be assigned 5, 5 and 6 subbands. A pilot IFDMA symbol or pilot LFDMA symbol for each transmitter may be generated as shown in FIG. 3A using a DFT-based configuration method.

  The pilot subband may be a subset of the data subband as described above with respect to FIGS. In general, the pilot subband may or may not be a subset of the data subband. Further, the pilot subbands can have the same or different (eg, wider) frequency spacing than the data subbands.

  In the above description, the data and pilot SC-FDMA symbols have the same duration, and each data SC-FDMA symbol and each pilot SC-FDMA symbol are transmitted in K + C sample periods. Different duration data and pilot SC-FDMA symbols may also be generated and transmitted.

FIG. 10 shows a transmission scheme 1000 with different data and pilot symbol durations. Each data SC-FDMA symbol with respect to the transmission scheme 1000 consists _{N D} output samples that are transmitted in _{N D} sample periods, and each pilot SC-FDMA symbol, _{N P} number of transmitted in _{N P} sample periods Consists of output samples. Here, N _D > 1, N _P > 1, and N _D ≠ N _P. For example _{N D} is also equal to K + C, _{N P} is also equal K / 2 + C, etc. K / 4 + C. K is equal to 512 as a specific example, C is equal to 32, _{N D} is equal to K + C = 544, also _{N P} may be be equal to K / 2 + C = 288. Each data SC-FDMA symbol may be a data IFDMA symbol that may be generated as shown in FIG. 3A or 3B, or a data LFDMA symbol that may be generated as shown in FIG. 3A, or data that may be generated as shown in FIG. 3A It may be an EFDMA symbol.

  As an example, the pilot SC-FDMA symbol may be half the duration of the data SC-FDMA symbol (not counting the cyclic prefix). In this case, there are K / 2 total “wider” subbands for the pilot, each wider subband having twice the width of the “normal” subband for traffic data.

  For shortened LFDMA symbols, the subband group consists of N / 2 wider subbands assigned indices 1 to N / 2. Transmitter 1 may be assigned a first subset of N / 4 wider subbands with even numbered indexes, and transmitter 2 may be assigned N / 4 numbered with odd numbered indexes. A second subset of wider subbands may be assigned. A shortened LFDMA symbol for the distributed pilot may be generated as follows.

  1. Form an original sequence of N / 4 pilot symbols.

  2. DFT is performed on N / 4 pilot symbols to obtain N / 4 frequency domain values.

  3. Map N / 4 frequency domain values to N / 4 wider subbands in the assigned subset and map zero values to the remaining wider subbands.

  4). A K / 2 point IDFT is performed on K / 2 frequency domain values and zero values to obtain a sequence of K / 2 time domain output samples.

  5. A cyclic prefix is added to the time domain sequence to generate a shortened pilot LFDMA symbol.

  For LFDMA, pilot and data from transmitters 1 and 2 are sent on the same subband group. The N / 2 wider pilot subbands occupy the same portion of the system bandwidth as the N normal data subbands. For IFDMA, there is no direct mapping (mapping) between a wider pilot subband and a normal data subband for a given interlace. N wider pilot subbands can be formed with two interlaces and can be assigned to four transmitters assigned to these two interlaces. Each of the four transmitters may be assigned N / 4 wider pilot subbands that are evenly spaced across the system bandwidth. Each transmitter is a shortened IFDMA symbol for a distributed pilot, eg, for a shortened pilot LFDMA symbol as described above, except that N / 4 frequency domain values are mapped to different wider pilot subbands. Can be generated.

  Transmission scheme 1000 may be used to reduce the amount of overhead for the pilot. For example, a single pilot symbol period having a duration shorter than the data symbol period may be assigned for pilot transmission. Transmission scheme 1000 can also be used in combination with CDM. Multiple (L) pilot symbol periods with shorter durations may be allocated for pilot transmission, where L is the length of the orthogonal code used for the CDM pilot.

  For clarity, TDM, CDM, distributed and localized pilot schemes have been described above, particularly for the simple case with two transmitters. In general, these pilot schemes can be used for any number of transmitters. For a TDM pilot scheme, Q transmitters can be assigned Q different symbol periods used for pilot transmission, and each transmitter can be assigned on its assigned symbol period. Can send a pilot. For the CDM pilot scheme, Q transmitters can be assigned Q different orthogonal codes for pilot transmission, and each transmitter can use its assigned orthogonal code to Pilot can be transmitted. For distributed IFDMA pilots, one interlace includes approximately N / Q subbands where each subset can be distributed across all K subbands and spaced apart by Q · S subbands. It can be divided into Q subsets. For distributed LFDMA pilots, a subband group may be divided into Q subsets that include approximately N / Q subbands where each subset may be spaced apart by Q subbands. For localized IFDMA pilots, one interlace includes approximately N / Q subbands where each subset can be evenly distributed across K / Q subbands and spaced by S subbands. It can be divided into Q subsets. For localized LFDMA pilots, one subband group may be divided into Q subsets, each subset containing approximately N / Q adjacent subbands. In general, Q may or may not be an integer divisor of N, and each transmitter may be assigned any number of subbands, and of the subbands in a given subband set. Any subband can be assigned. With respect to the distributed and localized pilot scheme, each transmitter can transmit its pilot on its assigned subset of subbands.

Pilot symbols used to generate pilot SC-FDMA symbols may be selected from modulation schemes such as M-PSK, M-QAM, and so on. The pilot symbols may also be derived based on a polyphase sequence, which is a sequence with good time characteristics (eg, constant time domain envelope) and good spectral characteristics (eg, flat frequency spectrum). For example, pilot symbols can be generated as follows.

Where n = 1,..., P
Here, P is the number of pilot symbols. P is equal to N for the TDM and CDM pilot schemes shown in FIGS. 5 and 6, respectively, and N / 2 for the exemplary distributed and localized pilot schemes shown in FIGS. 8A-9B. The phase ψ _n can be derived based on any one of the following:

  In equation (6), Q 'and P are relatively prime. Equation (3) relates to the Golomb sequence, Equation (4) relates to the P3 sequence, Equation (5) relates to the P4 sequence, and Equation (6) relates to the Chu sequence. These P3, P4 and Chu sequences can have any length.

Pilot symbols may also be generated as follows.

The phase ψ _{l, m} can be derived based on any one of the following, where l = 1,..., T and m = 1,.

Equation (8) relates to the Frank sequence, Equation (9) relates to the P1 sequence, and Equation (10) relates to the Px sequence. The lengths of the Frank, P1 and Px sequences are constrained to be P = T ² . Here, T is a positive integer.

  FIG. 11 shows a process 1100 performed by a transmitter to transmit pilot and data in a Q-FDMA system. A set of N subbands selected from the S subband sets is determined (block 1110). This subband set may include (1) data subbands used for data transmission or (2) pilot subbands shared by multiple transmitters for pilot transmission. For distributed or localized pilots, a subset of P subbands assigned for pilot transmission selected from among the Q subband subsets formed by the assigned subband set is determined ( Block 1112). For TDM or CDM pilots, the subset of subbands allocated for pilot transmission is equal to the set of subbands allocated for transmission and P = N. For distributed or localized pilots, Q> 1, and P may be equal to N / Q. Subband sets and subband subsets are: (1) whether distributed or localized pilots are being transmitted, or (2) whether IFDMA, LFDMA, EFDMA or hybrid IFDMA / LFDMA / EFDMA is being used by the system, Or (3) may be defined differently depending on whether the data and pilot SC-FDMA symbols have the same or different durations, etc. Blocks 1110 and 1112 may be performed for each time slot if the Q-FDMA system utilizes frequency hopping.

  A sequence of pilot symbols is generated based on, for example, a polyphase sequence (block 1114). This sequence typically includes one pilot symbol for each subband used for pilot transmission. For example, the sequence may include N pilot symbols for TDM or CDM pilots with N pilot subbands and N / 2 pilot symbols for distributed or localized pilots with N / 2 pilot subbands. Can be included. Data symbols are also generated in the usual manner (block 1116).

  Pilot SC-FDMA symbols are generated by the sequence of pilot symbols and such that these pilot symbols occupy subbands used for pilot transmission (block 1118). Data SC-FDMA symbols are generated by the data symbols and such that these pilot symbols occupy the subbands used for transmission (block 1120). For CDM pilots, a number of scaled pilot SC-FDMA symbols are generated based on the pilot SC-FDMA symbols and the orthogonal code assigned to the transmitter. Data SC-FDMA symbols are multiplexed with pilot SC-FDMA symbols using, for example, TDM as shown in FIG. 5 or 7 or using CDM as shown in FIG. 6 (block 1122). The multiplexed data and pilot SC-FDMA symbols are transmitted on the assigned time / frequency block (block 1124).

2. Channel Estimation Referring back to FIG. 1, the channel estimator for each receive antenna 152 at the receiver 150 estimates the channel response between each transmitter and this receive antenna. Many (Q) transmitters may share the same time / frequency block and multiplex these pilots using TDM, CDM, IFDM, or LFDM as described above. Each channel estimator performs complementary demultiplexing (demultiplexing) to derive a channel estimate for each of the Q transmitters sharing this time / frequency block.

  FIG. 12 shows a process 1200 performed by a channel estimator for one receive antenna to estimate a radio channel response for each transmitter based on pilots received from each transmitter. The channel estimation for one time / frequency block shared by the Q transmitters for clarity is described below.

  The channel estimator receives SC-FDMA symbols for the associated antenna in each symbol period and cancels the TDM or CDM performed on the pilot (block 1210). For the TDM pilot scheme shown in FIG. 5, Q received pilot SC-FDMA symbols are acquired during Q symbol periods from Q transmitters and received for each transmitter. Are processed to derive a channel estimate for this transmitter. With respect to the CDM pilot scheme shown in FIG. 6, Q received SC-FDMA symbols including CDM pilots from Q transmitters are multiplied with Q orthogonal codes assigned to these transmitters, Q Accumulated to obtain Q received pilot SC-FDMA symbols for a number of transmitters. For the distributed and localized pilot schemes shown in FIGS. 7-9B, one received pilot SC-FDMA symbol can be obtained in one symbol period for Q transmitters, and this received pilot SC. -FDMA symbols are processed to derive a channel estimate for each of the Q transmitters.

  The channel estimator removes the cyclic prefix in each received SC-FDMA symbol and obtains K input samples for this received SC-FDMA symbol (block 1212). The channel estimator then performs a K-point DFT on the K input samples for each received SC-FDMA symbol to obtain K frequency domain received values for the received SC-FDMA symbol (block 1214). The channel estimator performs channel estimation on received pilot values obtained from the received pilot SC-FDMA symbol (s). The channel estimator also provides RX data processor 160 with received data values obtained from received data SC-FDMA symbols. Channel estimation for one transmitter m is described below for clarity.

The pilots from the Q transmitters are orthogonal to each other for use of TDM, CDM, IFDM or LFDM. The received pilot value for transmitter m may be given as follows:

Where P _m (k) is the pilot value sent by transmitter m on subband k, and H _{m, r} (k) is the radio between transmitter m and receive antenna r for subband k. The complex gain for the channel,

Is the received pilot value from receive antenna r for subband k, N _r (k) is the noise on receive antenna r for subband k, and K _p is a subset of P pilot subbands It is.

For simplicity, the noise can be assumed to be additive white Gaussian noise (AWGN) with zero mean and variance N ₀ .

  The K-point DFT at block 1214 provides K received values for all K subbands. Only P received pilot values for the P pilot subbands used by transmitter m are retained, and the remaining KP received values are discarded (block 1216). P is equal to N for TDM and CDM pilot schemes and N / Q for distributed and localized pilot schemes. Different pilot subbands are used for TDM, CDM, distributed and localized pilot schemes, and thus different received pilot values are maintained for different pilot schemes. Further, different pilot subbands are used by different transmitters for distributed and localized pilot schemes, and thus different received pilot values are maintained for different transmitters.

The channel estimator may estimate the channel frequency response for transmitter m using various channel estimation techniques such as MMSE techniques, least squares (LS) techniques, and so on. The channel estimator is P based on the P received pilot values for the P pilot subbands and using these MMSE or LS techniques for the P pilot subbands used by transmitter m. A channel gain estimate of is derived (block 1218). For the MMSE technique, an initial frequency response estimate can be derived based on the received pilot values as follows.

here

Is the channel gain estimate between transmitter m and receive antenna r for subband k, and “*” represents the complex conjugate. For the LS technique, an initial frequency response estimate can be derived as follows.

The initial frequency response estimate includes P channel gains for the P pilot subbands. The impulse response of the radio channel can be characterized by L taps. Here, L may be smaller than P. A channel impulse response estimate for transmitter m may be derived based on the P channel gain estimates and using least squares (LS) or MMSE techniques (block 1220). L tap when n = 1,..., L,

Can be derived based on the initial frequency response estimate as follows.

here

Is

Or

A P × 1 vector containing W _PxL is a _submatrix of the Fourier matrix W _kxk ,

Is

L × 1 vector including “H” represents a conjugate transpose matrix.

The Fourier matrix W _kxk is defined such that the (u, v) th entry f _{u, v} is given below.

W _PxL includes P rows of W _kxk corresponding to P pilot subbands. Each row of W _PxL includes the first L elements of the corresponding row of W _kxk.

Contains L taps of the least squares channel impulse response estimate.

L tap,

An MMSE channel impulse response estimate with can be derived as follows.

here

Is an L × L autocovariance matrix of noise and interference. Regarding AWGN,

Is

Can be given as Here, N ₀ is noise variance. P-point IDFT may also be performed on the initial frequency response estimate to obtain a channel impulse response estimate with P taps.

  The channel estimator may perform filtering and / or post-processing on the initial frequency response estimate and / or the channel impulse response estimate to improve the quality of the channel estimate (block 1222). This filtering may be based on a finite impulse response (FIR) filter, an infinite impulse response (IIR) filter, or some other type of filter. In one embodiment, truncation may be performed to keep only the first L taps of the channel impulse response estimate and replace the remaining taps with zeros. In another embodiment, threshold setting may be performed to eliminate channel taps having lower energy below a predetermined threshold. This threshold may be calculated based on the energy of all P taps of the channel impulse response estimate, or simply the first L taps. In yet another embodiment, tap selection may be performed to keep the B best channel taps and erase the remaining channel taps.

  The channel estimator (1) zero-pads the L-tap or P-tap channel impulse response estimate to length N and (2) performs an N-point DFT on the expanded impulse response estimate To derive a final frequency response estimate for the N subbands in the time / frequency block (block 1224). The channel estimator may also (1) interpolate P channel gain estimates, or (2) perform a least squares approximation to the P channel gain estimates, or (3) other approximation techniques. Can be used to derive a final frequency response estimate for the N subbands.

  The frequency response estimate and / or channel impulse response estimate for the wireless channel may also be obtained in other ways using other channel estimation techniques.

3. Spatial Multiplexing Referring back to FIG. 1, a single input multiple output (SIMO) channel is formed between the single antenna of each transmitter 110 and the R antennas of receiver 150. The SIMO channel for transmitter m, where m = 1,..., M is the R × 1 channel response vector for each subchannel

And can be represented as follows:

Here, h _{m, r} (k, t) in the case of r = 1,. Between or complex channel gain. A different SIMO channel is formed between each transmitter and receiver. The channel response vectors for M transmitters 110a-110m are respectively

Can be shown as

If the number of transmitters selected for transmission (M) is less than or equal to the number of information channels in one channel set (or M ≦ S), then M transmitters have different information channels in one channel set. Can be assigned. If the number of transmitters exceeds the number of information channels in a channel set (or M> S), these transmitters can be assigned information channels from the minimum number of channel sets. The minimum number of channel sets (Q) required to support an M transmitter is

Can be given as here

Indicates a ceiling operator that provides an integer value greater than or equal to x. If multiple (Q) channel sets are used for M transmitters, each transmitter observes interference from at most Q-1 other transmitters at any given moment. , Orthogonal to at least M- (Q-1) other transmitters.

  For a Q-FDMA system, a maximum of Q transmitters can share a predetermined time / frequency block. For frequency hopping Q-FDMA systems, a given transmitter transmits on different subband sets in different time slots and transmits different time and frequency blocks over time due to the pseudo-random nature of frequency hopping. Shared with the machine. For simplicity, the following description is made with respect to one time / frequency block shared by transmitters 1-Q.

A multiple-input multiple-output (MIMO) channel is formed between Q transmitters sharing the same time and frequency block as the receiver 150. The MIMO channel is an R × Q channel response matrix for each subband in the time / frequency block.

And can be expressed as:

Here, K _d is a set of subbands related to the time / frequency block. In general, each transmitter may be equipped with one or multiple antennas. A multi-antenna transmitter can transmit different SC-FDMA symbol streams from multiple antennas, with each transmit antenna then

Would have a one-channel response vector of the form These multiple transmissions from multi-antenna transmitters can be processed in the same way as multiple transmissions from multiple single-antenna transmitters.

Each of the Q transmitters can transmit data and pilot using IFDMA, LFDMA, or EFDMA. The receiver 150 processes input samples from the R receive antennas to obtain received data values. The received data value for each subband k within each symbol period n of time slot t may be expressed as:

here

Is a Q × 1 vector with Q data values sent by Q transmitters on subband k in symbol period n of time slot t,

Is an R × 1 vector having R received data values obtained via R receive antennas for subband k in symbol period n of time slot t,

Is the noise vector for subband k within symbol period n of time slot t.

Channel response matrix for simplicity

Is assumed to be constant throughout the entire time slot and is not a function of the symbol period n.

N transmit vectors

Are formed by Q transmitters for N subbands in each symbol period n of time slot t. Each vector

Contains Q data values sent by Q transmitters on subband k in symbol period n of time slot t.

N received vectors

Is obtained for N subbands in each symbol period n of each time slot t. Each vector

Contains R data values obtained via R antennas at receiver 150 for one subband within one symbol period. For a given subband k, symbol period n and time slot t, a vector

The jth data value in is a vector

Channel response matrix to generate

Is multiplied by the j th vector / column. Sent by Q different transmitters

Q data values of Q vectors, one vector for each transmitter

To generate

Of the Q column. Vector obtained by receiver 150

Is Q vectors

Or

It consists of a linear combination of Therefore

Each received data value in

Of each of the Q transmitted data values. Thus, Q data values sent simultaneously by Q transmitters on each subband k within each symbol period n of time slot t interfere with each other at receiver 150.

  The receiver 150 can use various receiver spatial processing techniques to separate data transmissions sent simultaneously by Q transmitters on each subband within each symbol period. These receiver spatial processing techniques include zero-forcing (ZF) techniques, MMSE techniques, and maximum ratio combining (MRC) techniques.

The receiver 150 can derive a spatial filter matrix based on ZF, MMSE or MRC techniques as follows.

here

It is.

Receiver 150 may receive a channel response matrix for each subband based on pilots received from the Q transmitters.

Can be estimated. For clarity, the description here assumes that there is no channel estimation error. The receiver 150 then uses the estimated channel response matrix to derive a spatial filter matrix.

Is used.

Is assumed to be constant over time slot t, so the same spatial filter matrix can be used during all symbol periods in time slot t.

The receiver 150 can perform the following receiver spatial processing.

here

Is

May be equal to

Is an L × 1 vector with L detected data values for subband k in symbol period n of time slot t,

Is the noise after receiver spatial processing.

The detected data value is an estimate of the transmitted data value.

MMSE spatial filter

And MRC spatial filter

The estimate from is

Is the denormalized estimate of the data value at. Scaling matrix

Multiplication with provides a normalized estimate of the data value.

In general, different sets of transmitters are assigned different subband sets within a given time slot as determined by these hop patterns, for example. The S sets of transmitters assigned to the S subband sets within a given time slot may include the same or different numbers of transmitters. In addition, each transmitter set may include a single antenna transmitter, a multi-antenna transmitter, or a combination of both. Different sets of transmitters may also be assigned to a given subband set in different time slots. Channel response matrix for each subband in each time slot

Is determined by the set of transmitters using this subband in this time slot and includes one or more vectors / columns for each transmitter transmitting on this subband in this time slot. matrix

May include multiple vectors for one transmitter that uses multiple antennas to transmit different streams to receiver 150.

As indicated above, a number of data transmissions sent simultaneously by Q transmitters on each subband k in each symbol period n of each time slot t can be represented by these channel response vectors.

Can be separated by the receiver 150 based on these spatial signatures provided by. This allows the Q-FDMA system to enjoy higher capacity.

Q-FDMA may be used for the forward and reverse links. For the reverse link, multiple terminals can transmit simultaneously on the same time / frequency block to a multi-antenna base station that can separate transmissions from these terminals using the receiver spatial processing techniques described above. For the forward link, the multi-antenna base station can obtain channel estimates for all terminals (eg, based on pilots transmitted by these terminals) and performs transmitter spatial processing on transmissions sent to these terminals it can. For example, the base station can perform transmitter spatial processing for terminal m as follows.

here

Are data symbols sent to terminal m on subband k within symbol period n of time slot t,

Is an R × 1 vector with R transmitted symbols sent to terminal m via R antennas on subband k within symbol period n of time slot t.

Equation (24) shows transmitter spatial processing using MRC beamforming. The base station can also perform other types of transmitter spatial processing. For example, the base station can transmit to two users at the same time using zero forced beamforming, and there is another user at the beam zero for the first user, and this user is from the first user. Beams that do not observe interference can be formed.

  On the forward link, a multi-antenna terminal can receive transmissions from multiple base stations. Each base station can transmit to the terminal using a different hop pattern assigned to the terminal by the respective base station. Hop patterns assigned to terminals by different base stations may collide. Whenever this happens, the terminal can use receiver spatial processing to separate multiple transmissions sent simultaneously on the same subband within the same symbol period by these base stations.

  Q-FDMA can also be used to improve performance during handoff. Terminal A may be handed off from base station 1 to base station 2. At handoff, base station 2 can receive transmission from terminal A on a subband that overlaps a subband assigned to another terminal B communicating with base station 2. Base station 2 can perform receiver spatial processing to separate transmissions from terminals A and B. Base station 1 or 2 can also combine information (eg, detected data values) obtained by two base stations for terminal A to improve performance, known as “softer handoff”. Is a process to improve performance. Base stations 1 and 2 can also send orthogonal pilots to terminal A. The network may be designed such that the pilots for forward and / or reverse links in different sectors are orthogonal to each other.

  Orthogonal pilots can be sent on the forward and reverse links to facilitate channel estimation. Many terminals sharing the same time / frequency block can send orthogonal pilots to a given base station. Multiple base stations can also send orthogonal pilots to a given terminal, eg, at handoff. Orthogonal pilots can be sent using any of the pilot transmission schemes described herein.

4). H-ARQ Transmission Q-FDMA systems can use hybrid automatic repeat request (H-ARQ), also called incremental redundancy (IR) transmission. With H-ARQ, the transmitter sends one or multiple transmissions for a data packet until the packet is correctly decoded by the receiver or until the maximum number of transmissions has been sent. H-ARQ improves the reliability of data transmission and also supports rate adaptation for packets when channel conditions change.

  FIG. 13 shows H-ARQ transmission. The transmitter processes (eg, encodes and modulates) the data packet (packet 1) to generate multiple (B) data blocks, which may also be referred to as frames or subpackets. Each data block may contain sufficient information to allow the receiver to correctly decode the packet under suitable channel conditions. The B data blocks contain different redundancy information for the packet. Each data block can be sent in any number of time slots. In the example shown in FIG. 13, each data block is sent in one time slot.

  The transmitter transmits the first data block (block 1) for packet 1 in time slot 1. The receiver receives and processes (eg, demodulates and decodes) block 1, determines that packet 1 has been decoded in error, and sends a negative acknowledgment (NAK) to the transmitter in time slot 2. The transmitter receives the NAK and transmits the second data block (block 2) for packet 1 in time slot 3. The receiver receives block 2, processes blocks 1 and 2, determines that packet 1 is still decoded in error, and sends a NAK in time slot 4. Block transmission and NAK response can continue any number of times. In the example shown in FIG. 13, the transmitter transmits data block x (block x) related to packet 1 in time slot t with x ≦ B. The receiver receives block x, processes blocks 1-x for packet 1, determines that the packet has been decoded correctly, and returns an ACK in time slot 2b. The transmitter receives the ACK and ends the transmission of packet 1. The transmitter processes the next data packet (packet 2) and transmits a data block for packet 2 in a similar manner.

  In FIG. 13, there is one time slot delay for ACK / NAK response for each block transmission. To improve channel utilization, the transmitter can transmit a large number of packets in an interlaced manner. For example, the transmitter can transmit one packet in odd numbered time slots and another packet in even numbered time slots. More than two packets can also be interlaced during longer ACK / NAK delays.

  FIG. 13 shows transmission of both NAKs and ACKs. In the ACK-based scheme, the ACK is sent only if the packet is decoded correctly, NAKs are not sent, and are inferred by the absence of ACKs.

  FIG. 14 shows H-ARQ transmission for two transmitters a and b with frequency hopping. Each transmitter can transmit a new packet starting in any time slot. Each transmitter can also send any number of data blocks for each packet, and can send another packet when it receives an ACK for the current packet. Thus, packets transmitted by each transmitter appear asynchronous with respect to packets transmitted by other transmitters. By frequency hopping, each transmitter transmits on one sequence of time / frequency blocks. Each transmitter may interfere with other transmitters in a pseudo-random manner if these transmitters are assigned information channels in different channel sets as shown in FIG. Multiple transmitters can also interfere with each other within each time / frequency block if they are assigned the same information channel (not shown in FIG. 14).

  The receiver receives block transmissions from the transmitter and performs receiver spatial processing for each time / frequency block that has block transmissions from multiple transmitters. The receiver demodulates and decodes each packet based on all data symbol estimates obtained for all block transmissions received for each packet. For each correctly decoded packet, the H-ARQ transmission for this packet can be terminated, and the interference due to this packet can be caused by the input samples or the time / frequency block (s) used by this packet or Estimated from the received data value and removed. The interference estimate can be obtained, for example, by encoding and modulating the packet in the same manner performed by the transmitter and multiplying the resulting symbol by the channel estimate for the packet. The receiver was used by a correctly decoded packet to obtain a new data symbol estimate for a packet decoded in error and transmitted on the same time / frequency block as the correctly decoded packet Receiver spatial processing can be performed on the interference-removed symbols for all time / frequency blocks. Each packet that is decoded in error and at least partially overlaps any correctly decoded packet (ie shares some time / frequency block) is demodulated based on all data symbol estimates for this packet Can be decrypted.

5. Transmitter and Receiver FIG. 15 illustrates one embodiment of a transmitter 110m. Within TX data and pilot processor 120m, encoder 1512 receives traffic data, encodes each data packet based on an encoding scheme to generate encoded packets, and encodes each encoded packet into multiple data blocks. Divide into Interleaver 1514 interleaves or reorders each data block based on an interleaving scheme. A symbol mapper 1516 maps the interleaved bits in each data block to data symbols based on the modulation scheme. Pilot generator 1520 generates pilot symbols based on, for example, a polyphase sequence. TDM / CDM unit 1522 multiplexes data symbols with pilot symbols using TDM (eg, as shown in FIG. 5 or 7) or CDM (eg, as shown in FIG. 6). Data and pilot symbols can also be multiplexed after SC-FDMA modulation.

  Within controller / processor 140m, FH generator 1542 determines the set of subbands to use for transmission in each time slot based on, for example, the hop pattern assigned to transmitter 110m. For distributed and localized pilots, the controller / processor 140m also determines a subset of subbands to use for pilot transmission. For example, a transmitter assigned an information channel in channel set 1 may be assigned a first subset, and a transmitter assigned an information channel in channel set 2 may be assigned a second subset. The same applies hereinafter. SC-FDMA modulator 130m generates data SC-FDMA symbols such that the data symbols are sent on the set of subbands used for transmission. SC-FDMA modulator 130m also generates pilot SC-FDMA symbols such that pilot symbols are sent on a subset of subbands used for pilot transmission.

  FIG. 16 shows an embodiment of the receiver 150. At receiver 150, R DFT units 1610a-1610r receive input samples from receiver units 154a-154r, respectively, for the R antennas. Each DFT unit 1610 performs a DFT on the input samples for each symbol period to obtain a frequency domain value for each symbol period. R demultiplexer / channel estimators 1620a-1620r receive frequency domain values from DFT units 1610a-1610r, respectively. Each demultiplexer 1620 provides frequency domain values (or received data values) for data to K subband spatial processors 1632a-1632k.

Each channel estimator 1620 derives a channel estimate for each transmitter based on a frequency domain value (or received pilot value) for the pilot obtained for each transmitter. Spatial filter matrix calculation unit 1634 determines channel response matrix for each subband in each time slot based on channel response vectors for all transmitters using each subband and time slot

Form. Thereafter, the calculation unit 1634 may use the channel response matrix for each subband and time slot as described above

Spatial filter matrix for each subband of each time slot based on

To derive. Calculation unit 1634 provides K spatial filter matrices for the K subbands in each time slot.

  K subband space processors 1632a to 1632k obtain received data values for subbands 1 to K from demultiplexers 1620a to 1620r, respectively. Each subband spatial processor 1632 also receives a spatial filter matrix for that subband, performs receiver spatial processing on the received data values having the spatial filter matrix, and provides detected data values. During each symbol period, K spatial processors 1632 a-1632 k provide K vectors of detected data values for K subbands to a demultiplexer (Demux) 1636. Demultiplexer 1636 maps the detected data value for each transmitter to the detected SC-FDMA symbol. The detected SC-FDMA symbol for a given transmitter m is the SC-FDMA symbol received by receiver 150 for this transmitter with interference from other transmitters suppressed via receiver spatial processing. is there.

  SC-FDMA demodulator 170 processes each detected SC-FDMA symbol and provides a data symbol estimate to RX data processor 172. The SC-FDMA demodulator 170 may perform phase ramp equalization and removal for IFDMA, symbol demapping from allocated subbands, and the like. SC-FDMA demodulator 170 also maps the data symbol estimates for these M transmitters to M streams based on the information channels assigned to the M transmitters. FH generator 1642 determines the subbands used by each transmitter based on the hop pattern assigned to each transmitter.

  RX data processor 172 demaps, deinterleaves, and decodes the data symbol estimates for each transmitter and provides decoded data and decoding status for each decoded packet. Controller 180 may generate ACKs and / or NAKs based on the composite state, and return these ACKs and / or NAKs to the transmitter to control transmission of data blocks for H-ARQ.

  The techniques described herein may be implemented by various means. For example, these techniques can be implemented in hardware, software, or a combination thereof. For hardware implementation, the processing units used to perform pilot transmission, channel estimation, receiver spatial processing, etc. are one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), Digital signal processing devices (DSPDs), programmable (programmable) logic devices (PLDs), field programmable (user writable) gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, electronic devices, described herein It can be realized in other electronic units designed to perform the functions or combinations thereof.

  For software implementation, these techniques can be implemented by modules (eg, procedures, functions, etc.) that perform the functions described herein. The software code may be stored in a memory unit (eg, memory unit 142 or 182 of FIG. 1) and executed by a processor (eg, controller 140 or 180). The memory unit can be implemented inside the processor or outside the processor.

  Subheadings are included here for reference and to help you find some sections. These subheadings are not intended to limit the scope of the concepts described below, and these concepts may have applicability in other sections throughout this specification.

  The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be used in other embodiments without departing from the spirit or scope of the invention. It is applicable to. Accordingly, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features described herein.
Hereinafter, the invention described in the scope of claims of the present application will be appended.
[C1] Generate a sequence of pilot symbols, determine one set of subbands selected from at least two sets of subbands, determine a subset of subbands to use for pilot transmission, Single carrier frequency division multiple access (SC-FDMA) symbols by the one sequence of pilot symbols sent on one subset of subbands selected from at least two subsets of subbands formed by the one set of bands A processor that operates to generate
A memory connected to the processor;
A device comprising:
[C2] The one set of subbands comprises N subbands uniformly distributed across all K subbands, and the one subset of subbands is uniform across the N subbands. The apparatus according to C1, comprising P subbands distributed in, and where K, N and P are integers greater than one.
[C3] The apparatus of C2, wherein the processor is operative to generate interleaved frequency division multiple access (IFDMA) symbols with the one sequence of pilot symbols sent on the one subset of subbands.
[C4] The one set of subbands comprises N adjacent subbands among all K subbands, and the one subset of subbands is uniformly distributed across the N adjacent subbands The apparatus of C1, comprising P subbands, wherein K, N, and P are integers greater than one.
[C5] The apparatus of C4, wherein the processor is operative to generate a localized frequency division multiple access (LFDMA) symbol with the one sequence of pilot symbols sent on the one subset of subbands.
[C6] The set of subbands comprises N subbands uniformly distributed across all K subbands, and the one subset of subbands is P in the N subbands. Of C1, wherein K, N, and P are integers greater than one.
[C7] The apparatus of C6, wherein the processor is operative to generate interleaved frequency division multiple access (IFDMA) symbols with the one sequence of pilot symbols sent on the one subset of subbands.
[C8] The one set of subbands includes N adjacent subbands in all K subbands, and the one subset of subbands includes P adjacent subbands in the N subbands. And the apparatus according to C1, wherein K, N and P are integers greater than one.
[C9] The apparatus of C8, wherein the processor is operative to generate a localized frequency division multiple access (LFDMA) symbol with the one sequence of pilot symbols sent on the one subset of subbands.
[C10] The one set of subbands includes N subbands selected from among all K subbands, and the one subset of subbands is selected from among the N subbands. The apparatus of C1, comprising 1 subband, and wherein K, N and P are integers greater than one.
[C11] The processor replicates the one sequence of pilot symbols multiple times to generate one sequence extended by K pilot symbols, and applies a phase ramp to obtain a frequency-converted one sequence And the apparatus of C10, wherein the apparatus operates to add a cyclic prefix to the frequency transform sequence to generate an interleaved frequency division multiple access (IFDMA) symbol.
[C12] The processor performs a discrete Fourier transform (DFT) on the one sequence of pilot symbols to obtain frequency domain values, maps the frequency domain values to the subbands in the subset, and A zero value is mapped to the remaining subbands of all subbands, and an inverse discrete Fourier transform (IDFT) is performed on the frequency domain value and the zero value to obtain a sequence of time domain output samples, The apparatus of C10, operable to add a cyclic prefix to the sequence of time domain output samples to generate an SC-FDMA symbol.
[C13] The processor generates a data symbol, generates at least one SC-FDMA symbol for the data symbol, and converts the at least one SC-FDMA symbol for the data symbol to the SC-FDMA symbol for the pilot symbol. The apparatus of C1, which operates to perform time division multiplexing (TDM).
[C14] The processor operates to generate the one sequence of pilot symbols based on a polyphase sequence having a constant envelope in the time domain and having a flat spectral response in the frequency domain. The device according to C1.
[C15] The apparatus of C1, wherein the processor is operative to determine different sets of subbands for different time slots based on frequency hopping patterns.
[C16] The apparatus of C1, wherein the set of subbands is used for pilot transmission by a number of transmitters.
[C17] The multiple transmitters are multiple wireless devices, and the SC-FDMA symbols are orthogonal to at least one other SC-FDMA symbol generated by at least one other wireless device for pilot. , C16.
[C18] The multiple transmitters are multiple base stations, and the SC-FDMA symbols are orthogonal to at least one other SC-FDMA symbol generated by at least one other base station for pilot. , C16.
[C19] The apparatus of C1, wherein the one subset of subbands is used for pilot transmission and the one set of subbands is used for data transmission.
[C20] The apparatus of C1, wherein the multiple sets of subbands are used by multiple groups of transmitters for pilot transmission.
[C21] The apparatus of C1, wherein the orthogonal pilots are transmitted by transmitters in different sectors of the wireless network.
[C22] generating one sequence of pilot symbols;
Determining one set of subbands selected from at least two sets of subbands;
Determining a subset of subbands to be used for pilot transmission, the subband selected from at least two subsets of subbands formed by the one set of subbands;
Generating a single carrier frequency division multiple access (SC-FDMA) symbol with the sequence of pilot symbols sent on the subset of subbands;
A method comprising:
[C23] Generating the SC-FDMA symbol includes
The method of C22, comprising generating localized frequency division multiple access (LFDMA) symbols with the one sequence of pilot symbols sent on the one subset of subbands.
[C24] The generation of the SC-FDMA symbol includes:
The method of C22, comprising generating interleaved frequency division multiple access (IFDMA) symbols with the one sequence of pilots sent on the one subset of subbands.
[C25] Generating the SC-FDMA symbol includes
Duplicating the one sequence of pilot symbols multiple times to generate an extended sequence with K pilot symbols;
Applying a phase ramp to obtain a frequency transformed sequence;
Adding a cyclic prefix to the frequency transformed sequence to generate an interleaved frequency division multiple access (IFDMA) symbol;
The method according to C22, comprising:
[C26] The generation of the SC-FDMA symbol includes:
Performing a discrete Fourier transform (DFT) on the sequence of pilot symbols to obtain frequency domain values;
Mapping the frequency domain values to the subbands in the subset;
Mapping a zero value to the remaining subbands of the K total subbands;
Performing an inverse discrete Fourier transform (IDFT) on the frequency domain value and the zero value to obtain a sequence of time domain output samples;
Adding a cyclic prefix to the sequence of time domain output samples to generate the SC-FDMA symbol;
The method according to C22, comprising:
[C27] means for generating one sequence of pilot symbols;
Means for determining one set of subbands selected from at least two sets of subbands;
Means for determining a subset of subbands used for pilot transmission, the subband selected from among at least two subsets of subbands formed by said one set of subbands When,
Means for generating a single carrier frequency division multiple access (SC-FDMA) symbol by the one sequence of pilot symbols sent on the one subset of subbands;
A device comprising:
[C28] The means for generating the SC-FDMA symbol comprises:
The apparatus of C27, comprising means for generating a localized frequency division multiple access (LFDMA) symbol with the one sequence of pilot symbols sent on the one subset of subbands.
[C29] The means for generating the SC-FDMA symbol comprises:
The apparatus of C27, comprising generating interleaved frequency division multiple access (IFDMA) symbols with the one sequence of pilot symbols sent on the one subset of subbands.
[C30] The means for generating the SC-FDMA symbol comprises:
Means for replicating the sequence of pilot symbols multiple times to generate a sequence extended by K pilot symbols;
Means for applying a phase ramp to obtain a frequency converted sequence;
Means for adding a cyclic prefix to the frequency transformed sequence to generate an interleaved frequency division multiple access (IFDMA) symbol;
The apparatus according to C27, comprising:
[C31] The means for generating the SC-FDMA symbol comprises:
Means for performing a discrete Fourier transform (DFT) on the sequence of pilot symbols to obtain frequency domain values;
Means for mapping the frequency domain values to the subbands in the subset;
Means for mapping a zero value to the remaining subbands of the K total subbands;
Means for performing an inverse discrete Fourier transform (IDFT) on the frequency domain value and the zero value to obtain a sequence of time domain output samples;
Means for adding a cyclic prefix to the sequence of time domain output samples to generate the SC-FDMA symbol;
The method of C27, comprising:
[C32] generating one sequence of pilot symbols, determining one set of subbands selected from at least two sets of subbands, and depending on the one sequence of pilot symbols sent on the one set of subbands A processor that operates to generate single carrier frequency division multiple access (SC-FDMA) symbols and to multiplex the SC-FDMA symbols using time division multiplexing (TDM) or code division multiplexing (CDM) When,
A memory connected to the processor;
A device comprising:
[C33] The processor multiplexes SC-FDMA symbols into a symbol period designated for pilot transmission and data within at least one symbol period used for pilot transmission by at least one other transmitter. An apparatus according to C32, wherein the apparatus operates to transmit neither a pilot nor a pilot.
[C34] The processor generates at least two multiplied SC-FDMA symbols and one orthogonal code based on the SC-FDMA symbols, and at least two designated for pilot transmission by at least two transmitters. The apparatus of C32, operable to multiplex the at least two multiplied SC-FDMA symbols in one symbol period.
[C35] The processor generates a data symbol, generates at least one SC-FDMA symbol for the data symbol, and converts the at least one SC-FDMA symbol for the data symbol to the SC-FDMA symbol for the pilot symbol. The device of C32, which functions to multiplex with.
[C36] generating a sequence of pilot symbols;
Determining one set of subbands selected from at least two sets of subbands;
Generating a single carrier frequency division multiple access (SC-FDMA) symbol with the sequence of pilot symbols sent on the set of subbands;
Multiplexing the SC-FDMA symbol using time division multiplexing (TDM) or code division multiplexing (CDM);
A method comprising:
[C37] The multiplexing of the SC-FDMA symbols is as follows:
Generating at least two multiplied SC-FDMA symbols and orthogonal codes based on the SC-FDMA symbols;
Multiplexing the at least two scaled SC-FDMA symbols into at least two symbol periods designated for pilot transmission by at least two transmitters;
The method of C36, comprising:
[C38] means for generating a sequence of pilot symbols;
Means for determining one set of subbands selected from at least two sets of subbands;
Means for generating a single carrier frequency division multiple access (SC-FDMA) symbol by the one sequence of pilot symbols sent on the one set of subbands;
Means for multiplexing the SC-FDMA symbols using time division multiplexing (TDM) or code division multiplexing (CDM);
A device comprising:
[C39] The means for multiplexing the SC-FDMA symbol comprises:
Means for generating at least two multiplied SC-FDMA symbols and one orthogonal code based on the SC-FDMA symbols;
Means for multiplexing the at least two multiplied SC-FDMA symbols into at least two symbol periods designated for pilot transmission by at least two transmitters;
The apparatus of C38, comprising:
[C40] Generate pilot symbols and data symbols, generate at least one pilot single carrier frequency division multiple access (SC-FDMA) symbol for the pilot symbols, and at least one data SC-FDMA symbol for the data symbols Each pilot SC-FDMA symbol has a first symbol duration, each data SC-FDMA symbol has a second duration different from the first symbol duration, and the at least one A processor that operates to multiplex one pilot SC-FDMA symbol with the at least one data SC-FDMA symbol on one time slot used by at least two transmitters for data and pilot transmission;
A memory connected to the processor;
A device comprising:
[C41] The apparatus of C40, wherein the first symbol duration is shorter than the second symbol duration.
[C42] The processor generates at least two multiplied pilot SC-FDMA symbols and one orthogonal code based on the at least one pilot SC-FDMA symbol, and the at least two multiplied pilot SC-FDMA. The apparatus of C40, operable to multiplex symbols with at least two symbol periods designated for pilot transmission.
[C43] The processor multiplexes the at least one pilot SC-FDMA symbol into at least one symbol period designated for pilot transmission, and pilot transmission by the remaining transmitters of the at least two transmitters. The apparatus of C40, operable to transmit no data or pilot within at least one other symbol period used for.
[C44] The processor determines a set of subbands selected from at least two sets of subbands, and is a subset of the subbands used for pilot transmission, wherein the one set of subbands Determining a subset of subbands selected from among at least two subsets of the subbands formed by the pilot symbols sent on the one subset of subbands, the at least one pilot SC-FDMA symbol The apparatus according to C40, which operates to generate.
[C45] generating pilot symbols and data symbols;
Generating at least one pilot single carrier frequency division multiple access (SC-FDMA) symbol for the pilot symbol, each pilot single carrier frequency division multiple access (SC-FDMA) symbol having a first symbol duration; When,
Generating at least one data SC-FDMA symbol for the data symbol, each data SC-FDMA symbol having a second duration different from the first symbol duration;
Multiplexing the at least one pilot SC-FDMA symbol with the at least one data SC-FDMA symbol on a time slot used by at least two transmitters for data and pilot transmission;
A method comprising:
[C46] the multiplexing the at least one pilot SC-FDMA symbol with the at least one data SC-FDMA symbol;
Generating at least two multiplied pilot SC-FDMA symbols and one orthogonal code based on the at least one pilot SC-FDMA symbol;
Multiplexing the at least two multiplied pilot SC-FDMA symbols into at least two symbol periods designated for pilot transmission;
A method according to C45, comprising:
[C47] means for generating pilot symbols and data symbols;
To generate at least one pilot single carrier frequency division multiple access (SC-FDMA) symbol for the pilot symbol, each pilot single carrier frequency division multiple access (SC-FDMA) symbol having a first symbol duration. Means of
Means for generating at least one data SC-FDMA symbol for the data symbol, each data SC-FDMA symbol having a second duration different from the first symbol duration;
Means for multiplexing the at least one pilot SC-FDMA symbol with the at least one data SC-FDMA symbol on a time slot used by at least two transmitters for data and pilot transmission;
A device comprising:
[C48] the means for multiplexing the at least one pilot SC-FDMA symbol with the at least one data SC-FDMA symbol;
Means for generating at least two multiplied pilot SC-FDMA symbols and one orthogonal code based on the at least one pilot SC-FDMA symbol;
Means for multiplexing the at least two multiplied pilot SC-FDMA symbols into at least two symbol periods designated for pilot transmission;
The apparatus according to C47, comprising:
[C49] operates to receive at least one single carrier frequency division multiple access (SC-FDMA) symbol in one time slot used by at least two transmitters to send orthogonal pilot and non-orthogonal data transmissions At least one receiver unit;
And a processor operative to process the at least one SC-FDMA symbol to obtain channel estimates for the at least two transmitters.
[C50] The at least two transmitters include time division multiplexing (TDM), code division multiplexing (CDM), interleaved frequency division multiplexing (IFDM), localized frequency division multiplexing (LFDM), or a combination thereof. The apparatus according to C49, wherein the orthogonal pilot is transmitted using and the processor is operative to perform demultiplexing (demultiplexing) of the orthogonal pilot transmitted by the at least two transmitters. .
[C51] The processor operates to transform the at least one SC-FDMA symbol to obtain a frequency domain pilot value and derive a frequency response estimate for each transmitter based on the frequency domain pilot value. The device according to C49.
[C52] The processor is operative to derive the frequency response estimate for each transmitter based on the frequency domain pilot value and using a minimum mean square error (MMSE) or least squares (LS) technique. The apparatus according to C51.
[C53] The apparatus of C51, wherein the processor is operative to derive a channel impulse response estimate for each transmitter based on the frequency response estimate for each transmitter.
[C54] receiving at least one single carrier frequency division multiple access (SC-FDMA) symbol in one time slot used by at least two transmitters to transmit orthogonal pilot and non-orthogonal data transmissions;
Processing the at least one SC-FDMA symbol to obtain channel estimates for the at least two transmitters;
A method comprising:
[C55] The processing of the at least one SC-FDMA symbol comprises:
Transforming the at least one SC-FDMA symbol to obtain a frequency domain pilot value;
Deriving a frequency response estimate for each transmitter based on the frequency domain pilot value;
The method of C54, comprising:
[C56] means for receiving at least one single carrier frequency division multiple access (SC-FDMA) symbol in one time slot used by at least two transmitters to send orthogonal pilot and non-orthogonal data transmissions; ,
Means for processing the at least one SC-FDMA symbol to obtain channel estimates for the at least two transmitters;
A device comprising:
[C57] The means for processing the at least one SC-FDMA symbol comprises:
Means for converting the at least one SC-FDMA symbol to obtain a frequency domain pilot value;
Means for deriving a frequency response estimate for each transmitter based on the frequency domain pilot value;
The apparatus according to C56, comprising:
[C58] Receiving single carrier frequency division multiple access (SC-FDMA) symbols via multiple receive antennas and orthogonal pilots and non-orthogonal on a time / frequency block consisting of a set of subbands in multiple symbol periods A first processor operable to process the SC-FDMA symbol to obtain received data values for at least two transmitters sending data transmissions;
A second processor operative to perform receiver spatial processing on the received data values to obtain detected data values for the at least two transmitters;
A device comprising:
[C59] The first processor is operative to derive channel estimates for the at least two transmitters, and the second processor is configured to determine the first of the subbands based on channel estimates for the at least two transmitters. The apparatus of C58, wherein the apparatus is operative to derive a set of spatial filter matrices for the set and to perform receiver spatial processing based on the set of spatial filter matrices.
[C60] The second processor is operative to derive the set of spatial filter matrices based on a zero forcing (ZF) technique, a minimum mean square error (MMSE) technique, or a maximum ratio combining (MRC) technique, C59 The device described in 1.
[C61] The apparatus of C58, further comprising a third processor operative to perform SC-FDMA demodulation.
[C62] The controller of C58, further comprising a controller operable to determine the one set of subbands out of at least two sets of subbands based on a frequency hopping pattern assigned to the at least two transmitters. Equipment.
[C63] The apparatus of C58, further comprising a third processor operative to process data values detected for the at least two transmitters to obtain decoded data.
[C64] The third processor operates to determine the decoding state of each packet and provide an acknowledgment (ACK) for each correctly decoded packet, and the ACK is a value of the correctly decoded packet. The device according to C63, which is used to terminate the transmission.
[C65] The at least two transmitters include a first transmitter that communicates with a first base station in a wireless network and a second transmitter that communicates with a second base station in the wireless network; and The device of C58, wherein a device resides at the first base station.
[C66] the at least two transmitters include a first transmitter in communication with the first and second base stations, the apparatus resident in the first base station, and further
Obtaining a detection data value for the first transmitter from the second processor, obtaining a detection data value derived by the second base station for the first transmitter, and the first transmitter. The apparatus of C58, comprising a third processor that operates to combine detected data values obtained from the second processor and the second base station with respect to.
[C67] receiving a single carrier frequency division multiple access (SC-FDMA) symbol via a plurality of receive antennas;
Processing the SC-FDMA symbols to obtain received data values for at least two transmitters sending orthogonal pilot and non-orthogonal data transmissions on a one-time frequency block consisting of a set of subbands in a plurality of symbol periods; When,
Performing receiver spatial processing on the received data values to obtain detected data values for the at least two transmitters.
[C68]
Deriving channel estimates for the at least two transmitters;
Deriving a set of spatial filter matrices for the set of subbands based on channel estimates for the at least two transmitters, wherein the receiver spatial processing is based on the set of spatial filter matrices. The method according to C67, wherein
[C69] Deriving the set of spatial filter matrices includes:
The method of C68, comprising deriving the set of spatial filter matrices based on a zero forcing (ZF) technique, a minimum mean square error (MMSE) technique, or a maximum ratio combining (MRC) technique.
[C70] The method of C67, further comprising performing SC-FDMA demodulation on detected data values for the at least two transmitters.
[C71] means for receiving a single carrier frequency division multiple access (SC-FDMA) symbol via a plurality of receive antennas;
To process the SC-FDMA symbols to obtain received data values for at least two transmitters sending orthogonal pilot and non-orthogonal data transmissions on a one-time frequency block consisting of a set of subbands in a plurality of symbol periods Means of
Means for performing receiver spatial processing on the received data values to obtain detected data values for the at least two transmitters.
[C72]
Means for deriving channel estimates for the at least two transmitters;
Means for deriving a set of spatial filter matrices for the set of subbands based on channel estimates for the at least two transmitters, wherein the receiver spatial processing is the set of spatial filter matrices. The apparatus according to C71, executed on the basis of
[C73] The means for deriving the set of spatial filter matrices includes:
The apparatus of C72, comprising means for deriving the set of spatial filter matrices based on a zero forcing (ZF) technique, a minimum mean square error (MMSE) technique, or a maximum ratio combining (MRC) technique.
[C74] The apparatus of C71, further comprising means for performing SC-FDMA demodulation on the detected data values for the at least two transmitters.

Claims (18)

Placing the total number of available subbands in a set of a plurality of predetermined subbands that collectively constitute the total number of available subbands;
Dividing a set of subbands from the set of subbands into a plurality of subsets of the set of subbands, wherein each of the plurality of subsets includes at least two subbands;
Generating a first sequence of pilot symbols for a first pilot transmission in one subset of the set of subbands from among the plurality of subsets of the set of subbands; and A sequence of symbols is generated in a second processor for a second pilot transmission in another subset of the set of subbands from among the plurality of subsets of the set of subbands. is configured to sequence and Lee Ntaresu pilot symbols, should be noted that the at least one pilot symbol of the sequence of the first pilot symbol simultaneously on all of the at least two sub-bands of the associated subset is generated for transmission to the first pilot transmission perpendicular to the transmission the second pilot That,
Generating a first sequence of data symbols for a first data transmission that is non-orthogonal to a second data transmission of a second sequence of data symbols generated in the second processor ;
A first processor adapted to:
An apparatus comprising: a transmitter coupled to the first processor for transmitting the first pilot symbol sequence and the first data symbol sequence.   The apparatus of claim 1, wherein the first pilot symbol sequence is an SC-FDMA symbol.   The apparatus of claim 1, wherein the first sequence of data symbols is an SC-FDMA symbol. Placing the total number of available subbands in a set of predetermined subbands that collectively constitute the total number of available subbands;
Dividing a set of subbands from the set of subbands into a plurality of subsets of the set of subbands, wherein each of the plurality of subsets includes at least two subbands;
Generating a first sequence of pilot symbols in a first processor for a first pilot transmission in one subset of the set of subbands from among the plurality of subsets of the set of subbands; And the first sequence of pilot symbols is a second processor for second pilot transmission on another subset of the set of subbands from among the plurality of subsets of the set of subbands. is configured to sequence and Lee Ntaresu of the second pilot symbol generated in still, said at least one pilot symbol of the sequence of the first pilot symbol associated said at least two sub-subsets It is generated for transmission simultaneously on all bands, the first pilot transmission before It is orthogonal to the second pilot transmission,
Generating a first sequence of data symbols in the first processor for a first data transmission that is non-orthogonal to a second data transmission in a second sequence of data symbols generated in the second processor and that,
Transmitting the first pilot symbol sequence and the first data symbol sequence.   The method of claim 4, wherein the first pilot symbol sequence is an SC-FDMA symbol.   The method of claim 4, wherein the first sequence of data symbols is an SC-FDMA symbol. Means for placing the total number of available subbands in a set of a plurality of predetermined subbands that collectively constitute the total number of available subbands;
Means for dividing a set of subbands from among the plurality of subband sets into a plurality of subsets of the set of subbands, wherein each of the plurality of subsets includes at least two subbands; Including,
A first symbol for generating a first pilot symbol sequence for a first pilot transmission in one subset of the subband set from among the plurality of subsets of the subband set. Generator means and the first sequence of pilot symbols for a second pilot transmission in another subset of the set of subbands from among the plurality of subsets of the set of subbands; is configured to sequence and Lee Ntaresu of the second pilot symbol generated in second processor, we should be noted that the first of the at least one pilot symbol of the sequence of pilot symbols is related subset at least It is generated for transmission simultaneously on all of the two sub-bands, the first pilot transmission Serial second is orthogonal to the pilot transmission,
The first symbol generator means is first for a first data transmission that is non-orthogonal to a second data transmission of a second series of data symbols generated in the second symbol generator means. including means for generating a sequence of data symbols,
An apparatus comprising: means for transmitting the first pilot symbol sequence and the first data symbol sequence.   The apparatus of claim 7, wherein the first pilot symbol sequence is an SC-FDMA symbol.   8. The apparatus of claim 7, wherein the first sequence of data symbols is an SC-FDMA symbol. Placing the total number of available subbands in a set of a plurality of predetermined subbands that collectively constitute the total number of available subbands;
Dividing a set of subbands from the set of subbands into a plurality of subsets of the set of subbands, wherein each of the plurality of subsets includes at least two subbands;
Generating a first sequence of pilot symbols for a first pilot transmission in one subset of the set of subbands from among the plurality of subsets of the set of subbands; and A sequence of symbols is generated in a second processor for a second pilot transmission in another subset of the set of subbands from among the plurality of subsets of the set of subbands. is configured to sequence and Lee Ntaresu pilot symbols, should be noted that the at least one pilot symbol of the sequence of the first pilot symbol simultaneously on all of the at least two sub-bands of the associated subset is generated for transmission to the first pilot transmission perpendicular to the transmission the second pilot That,
Generating a sequence of first data symbols for the first data transmission is non-orthogonal to the second data transmission sequence of second data symbols generated in the second processor, is adapted to A first processor;
A multiplexer for multiplexing the sequence of the first pilot symbols;
An apparatus comprising: a transmitter coupled to the first processor for transmitting the first pilot symbol sequence and the first data symbol sequence.   The apparatus of claim 10, wherein the first sequence of pilot symbols is an SC-FDMA symbol.   The apparatus of claim 10, wherein the first sequence of data symbols is an SC-FDMA symbol. Placing the total number of available subbands in a set of predetermined subbands that collectively constitute the total number of available subbands;
Dividing a set of subbands from the set of subbands into a plurality of subsets of the set of subbands, wherein each of the plurality of subsets includes at least two subbands;
Generating a first sequence of pilot symbols in a first processor for a first pilot transmission in one subset of the set of subbands from among the plurality of subsets of the set of subbands; And the first sequence of pilot symbols is a second processor for second pilot transmission on another subset of the set of subbands from among the plurality of subsets of the set of subbands. is configured to sequence and Lee Ntaresu of the second pilot symbol generated in still, said at least one pilot symbol of the sequence of the first pilot symbol associated said at least two sub-subsets It is generated for transmission simultaneously on all bands, the first pilot transmission before It is orthogonal to the second pilot transmission,
Generating a first sequence of data symbols in the first processor for a first data transmission that is non-orthogonal to a second data transmission in a second sequence of data symbols generated in the second processor and that,
Multiplexing the first pilot symbol sequence;
Transmitting the first pilot symbol sequence and the first data symbol sequence.   The method of claim 13, wherein the first sequence of pilot symbols is an SC-FDMA symbol.   The method of claim 13, wherein the first sequence of data symbols is an SC-FDMA symbol. Means for placing the total number of available subbands in a set of a plurality of predetermined subbands that collectively constitute the total number of available subbands;
Means for dividing a set of subbands from among the plurality of subband sets into a plurality of subsets of the set of subbands, wherein each of the plurality of subsets includes at least two subbands; Including,
A first symbol for generating a first pilot symbol sequence for a first pilot transmission in one subset of the subband set from among the plurality of subsets of the subband set. Generator means and the first sequence of pilot symbols for a second pilot transmission in another subset of the set of subbands from among the plurality of subsets of the set of subbands; is configured to sequence and Lee Ntaresu of the second pilot symbol generated in second processor, we should be noted that the first of the at least one pilot symbol of the sequence of pilot symbols is related subset at least It is generated for transmission simultaneously on all of the two sub-bands, the first pilot transmission Serial second is orthogonal to the pilot transmission,
The first symbol generator means is configured to transmit first data for a first data transmission that is non-orthogonal to a second data transmission of a second series of data symbols generated in a second symbol generator. including means for generating a sequence of symbols,
Means for multiplexing the first sequence of pilot symbols;
An apparatus comprising: means for transmitting the first pilot symbol sequence and the first data symbol sequence.   The apparatus of claim 16, wherein the first sequence of pilot symbols is an SC-FDMA symbol.   The apparatus of claim 16, wherein the first sequence of data symbols is an SC-FDMA symbol.

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